Fun was a concept.
History
When asked for his name, rank, and intention at Bowie Base One, the Tenth Doctor responded, "The Doctor, doctor, fun." (TV: The Waters of Mars [+]Loading...["The Waters of Mars (TV story)"])
The Eleventh Doctor once wrote in his diary that from 10am - 11am, he watched The Story of Tricey Beaker and Bear With Me on TV, which he described as "fun". (PROSE: The Doctor's Diary [+]Loading...{"page":"15","1":"The Doctor's Diary (DWA 308 short story)"})
Ruby Sunday once recalled that the fun "really began" on her first trip with the Doctor, recounting their brief visit to see some dinosaurs and their visit to Baby Station Beta. (PROSE: The Bogeyman [+]Loading...{"page":"20-21","1":"The Bogeyman (short story)"})
Among the last humans to have lived on Earth, Cassandra O'Brien.Δ17 recalled that her mother and father had a "little house" built into the side of the Los Angeles Crevasse, where she had fun. (TV: The End of the World [+]Loading...["The End of the World (TV story)"])
Although some acts of the Crew of the Copper-Colored Cupids were relatively amoral, the individuals who knew the Crew personally didnt hold it against them, as they couldn’t help themselves and were "jolly good fun to be around.". This was once recalled by the Bookwyrm. (PROSE: Previously On... The Multiverse [+]Loading...{"page":"19-22","1":"Previously On... The Multiverse (short story)"})
Behind the scenes
In non-valid sources
After tricking the Tenth Doctor into thinking he'd returned his DVD copy of Schwarzenegger to Arnie's Videos 400 years late, and demanding four million pounds, leading the Doctor to disappear, Arnold Schwarzenegger reflected that the Doctor hadn't been late in the first place, and that he loved having fun with "those crazy Time Lords". (TV: Series 1 Episode 6 [+]Loading...["Series 1 Episode 6 (Hedz TV story)"])
The Doctor's expertise was once listed as including telebiogenesis, conkers, gravitic anomalisation, having fun, the Mikado, Nothern Soul, and The Beano. (WC: Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract [+]Loading...["Tom Baker stars in John Lloyd's lost Doctor Who adventure, The Doomsday Contract (webcast)"])
After the potato pie they'd tried to bake burnt in just fifteen seconds due to them travelling at light speed in the STARSHED, and the Alien King of Splargle was due to arrive expecting dinner in thirty, Doctor Doctor remarked to Poppy O'Toole that "time flies when you're having fun", to which she replied that she wouldn't know. (TV: The Alien King of Splargle comes for tea! [+]Loading...["The Alien King of Splargle comes for tea! (TV story)"])